The results from a flow cytometer analysis of microscopic particles often depend on a sample fluid prepared by a machine and/or an experimenter. Errors in the preparation of the sample fluid may drastically alter the accuracy and conclusion of the flow cytometer analysis. As a real world example, CD4 tests are used in determining the state of the immune system of a patient and the progression of HIV to AIDS. A CD4 count of 200 or lower is used to indicate that a patient with HIV has AIDS. During this determination, reference beads are added to a blood sample, and counted by a flow cytometer to calculate the volume of blood analyzed by the flow cytometer. The calculated volume of blood and the number of CD4 particles analyzed during the flow cytometer test are used to calculate the CD4 count. An improperly prepared blood sample, such as one where the concentration of reference beads is not as expected, can lead to false positives and a misdiagnosis. Thus, there is a need in the flow cytometer field to create a new and useful system and method for verification of a prepared sample. This invention provides such a new and useful system and method.